From: Keith David Bershatsky <esq@lawlist.com>
To: Martin Rudalics <rudalics@gmx.at>, Eli Zaretskii <eliz@gnu.org>,
Stefan Monnier <monnier@iro.umontreal.ca>
Cc: 19684@debbugs.gnu.org
Subject: bug#19684: 25.0.50; `this-command` is set to `nil` before `window-scroll-functions` hook runs.
Date: Sun, 25 Jan 2015 09:42:44 -0800 [thread overview]
Message-ID: <m24mre3gff.wl%esq@lawlist.com> (raw)
In-Reply-To: <m2ppa3xr6z.wl%esq@lawlist.com>
Thank you (Eli, Stefan and Martin) for helping me to better understand how the redisplay process works.
I was surprised to learn that I could not depend upon either `this-command` or `last-command` when using the `window-scroll-functions` hook because a forced redisplay prior thereto -- e.g., `(redisplay)` -- makes a difference in the values.
To obtain the name of the interactive function that ran before the `window-scroll-functions` hook was triggered:
`this-command` may be used in the `window-scroll-functions` when there IS a forced redisplay prior thereto.
`last command` may be used in the `window-scroll-functions` when there is NOT a forced redisplay prior thereto.
I am unaware of any documentation that could have helped me to discover the behavior described above. Perhaps the Emacs team might consider adding something to the doc-string and/or the manual so that a user is advised as to the behavior, and to suggest an alternative approach:
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
(defvar my-command nil)
(defun set-my-command ()
(setq my-command this-command))
(add-hook 'post-command-hook 'set-my-command)
(defun wsf-fn (win _start)
"NOTE: Since the `window-scroll-functions` hook may be called more than
once, the user may not wish to set `my-command` to `nil` at this time."
(message "my-command: %s | this-command: %s | last-command: %s"
my-command this-command last-command)
(setq my-command nil))
(add-hook 'window-scroll-functions-hook 'wsf-fn)
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
Thanks,
Keith
next prev parent reply other threads:[~2015-01-25 17:42 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-01-25 7:19 bug#19684: 25.0.50; `this-command` is set to `nil` before `window-scroll-functions` hook runs Keith David Bershatsky
2015-01-25 10:38 ` martin rudalics
2015-01-25 15:33 ` Eli Zaretskii
2015-01-25 16:14 ` Stefan Monnier
2015-01-25 17:42 ` Keith David Bershatsky [this message]
2019-10-01 20:16 ` Stefan Kangas
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